Swim fin



FIG. 1 is a top perspective view of a swim fin, showing my new design;

FIG. 2 is a front-elevational view thereof;

FIG. 3 is a rear-elevational view thereof;

FIG. 4 is a bottom-plan view thereof; and

FIG. 5 is a side-elevational view of the side not seen in FIG. 1. 

The ornamental design for a swim fin, as shown and described. 